1. Field of the Invention
The present invention relates to a method and an apparatus for elevator group control by which an elevator system including a plurality of elevator cars and a plurality of destination floors are controlled.
2. Description of the Background Art
Recently, an elevator system including a plurality of elevator cars and a plurality of destination floors is equipped with a microcomputer to administer efficient and speedy allocations of elevator cars to hall calls produced at various destination floors, so as to improve the efficiency of elevator utilization and the quality of service.
Namely, in such an elevator system, when a hall call is produced at a certain floor, an elevator car which is most appropriate to respond to this hall call is selected from the plurality of elevator cars of the system, while the other elevator cars are prohibited to respond to this hall call. Meanwhile, at the hall of the floor from which the hall call is produced, an allocation indication lamp provided in a vicinity of an elevator entrance of the allocated elevator turns on, and an approach of the allocated elevator car is notified by a ringing of a chime and a flashing of the allocation indication lamp.
More recently, due to the development in the field of a micro-computer, such an elevator system is equipped with a function to collect in real time various data such as elevator car call response registration data regarding hall calls to which each elevator car has responded, so as to apprehend traffic demands among the floors of each building, and the elevator group control apparatus utilizes these data to the elevator car allocation control, so as to account for a unique situation characteristic to each building.
Such a conventional elevator group control apparatus is shown in FIG. 1.
This elevator group control apparatus comprises: a group control unit 101 and a plurality (N in number) of elevator car control units 102-1 to 102-N provided in correspondence with N elevator cars incorporated in the elevator system, which are connected through a high speed data transmission line 106.
The apparatus also includes hall call buttons 103 provided on each floor of a building in which the elevator system operates, hall call control units 104 provided for each hall call buttons 103 at each floor, and a monitor unit 105. These hall call control units 104 are connected with the group control unit 101 and elevator car control units 102-1 to 102-N through a low speed data transmission line 107.
The group control unit 101 is usually located in a monitoring room, but a recent elevator system also has a sub group control unit provided in one of the elevator unit of the elevator system, in addition to the main group control unit in the monitoring room, such that this sub group control unit can be substituted for the main group control unit in a case the main group control unit fails.
Next, the operation of this elevator group control apparatus of FIG. 5 will be described.
When a user presses one of the hall call buttons 103 at an n-th floor of the building, the corresponding hall call control unit 104 on the n-th floor sends a hall call signal to the group control unit 101. In response to the reception of this hall call signal from the hall call control unit 104, the group control unit 101 detects the current positions of each elevator car, calculates the estimated response time (an estimated time for an elevator car to reach the n-th floor plus a time elapsed since the hall call has been produced) for each elevator car, and allocates the most appropriate elevator car having a smallest estimated response time to this hall call at the n-th floor.
Here, if the most appropriate elevator car selected by the group control unit 101 is an elevator car No. 1 controlled by the elevator car control unit 102-1, the group control unit 101 sends a command signal for activating this elevator car No. 1 to the elevator car control unit 102-1, while giving a notice signal for notifying that the elevator car No. 1 has been allocated to the hall call control unit 104 at the n-th floor. In response to the reception of this notice signal from the group control unit 101, the hall call control unit 104 at the n-th floor turns on the allocation indication lamp provided in a vicinity of an elevator entrance of the elevator car No. 1, so that the user on the n-th floor can recognize that the elevator car No. 1 is coming in response to the hall call he produced.
Now, in a kind of building which has restaurants on a particular floor, the traffic demands to this floor sharply increases during a particular period of time such as a first half of a lunch break period. For this reason, much higher transport efficiency is required in such a building especially during such a particular period of time. Here, a case of the higher transport efficiency means a case such as that in which, while each elevator car is moving to the particular floor, the intervening floors from which the hall calls are produced and to which this elevator car has been allocated are not passed by for the reason that this elevator car is full, and yet by the time this elevator car reaches to the particular floor, this elevator car is at least nearly full.
In a conventional elevator group control apparatus, such a higher transport efficiency is achieved by estimating a weight to be given to each floor which indicates how important it is for an elevator car to stop at that floor for the sake of a total transport efficiency, in addition to the aforementioned estimated response time, so as to prevent the occurrence of a case in which the elevator car passes by a floor at which it is scheduled to stop for the reason that the elevator car has already been full, as much as possible. In other words, the elevator cars of the elevator system are controlled such that all the elevator cars carry nearly equal number of passengers.
However, such an estimation of a number of passengers in each elevator car is based on a statistical method, so that it cannot account for continuously changing situations around the halls of the elevator system accurately. As a consequence, the conventional elevator group control apparatus often created a situation in which there are many users are kept waiting on several floors, while the elevator cars are reaching to the particular floor with much less than a full number of passengers.
Such a situation will now be described in detail, with reference to FIG. 2.
A situation shown in FIG. 2 is that in which three elevator cars No. 1 to No. 3 are operating between the first floor and the tenth floor, and the hall calls to go to the first floor on which the restaurants are located has been produced at the sixth, ninth, and tenth floors, where each of these floors has a large number of users waiting.
In this FIG. 2, black triangles marked on a passages of the elevator car No. 3 at the sixth, ninth, and tenth floors indicate the hall calls produced at respective floors, while a black dot marked on a passage of each elevator car at various floors indicate the next destination of each elevator car.
Thus, the elevator car No. 1, on which less than a full number of passengers are aboard, is stopping at that moment at the fifth floor in response to the hall call produced at that floor, and is destined to the first floor next, as a passage between the fifth floor and the first floor is designated as an express zone in this building. Consequently, the elevator car No. 1 will reach the first floor with less than a full number of passengers aboard.
Meanwhile, the elevator car No. 2 is descending to the first floor with a full number of passengers aboard, while the elevator car No. 3 is ascending from the first floor to the fourth floor to which the car call has been made.
In this situation, all the hall calls produced at the sixth, ninth, and tenth floors are allocated to the elevator car No. 3, and yet it takes a considerable amount of time for this elevator car No. 3 to serve all these floors, so that the quality of service with respect to the many users waiting on the sixth, ninth, and tenth floors is very low.
Here, in order to improve the transport efficiency, there is an idea to change the allocation of the elevator car No. 3 with respect to the sixth floor to the elevator car No. 1 while the elevator car No. 1 was still located above the sixth floor level, so that the elevator car No. 1 serves the users at the sixth floor fitst, and then stops at the fifth floor to serve the users at the fifth floor, before descending to the first floor.
However, if such a change of allocation is performed, there appears a possibility that the elevator car No. 1 becomes full at the sixth floor, so that it has to pass by the fifth floor despite of the hall call allocation. In such a situation, the priority rights of the users at the fifth floor to whom the elevator car No. 1 had been allocated before the hall call was produced at the sixth floor are unjustly neglected. Thus, even if the transport efficiency can be improved by this method, the overall quality of service has to be severely lowered, and for this reason it is practically impossible to adapt such a method.